clarke



{No Model.) 2 Sheets-Sheet 1. T. G. CLARKE.

GANTILEVEP. BRIDGE. No. 504,559. Patented Sept. 5, 1893.

W/TNESSES. A lNVENTOH (190.75% 6% BY j U W 6 ATTORNEYS.

UNITED STATES PATENT OFFICE.

THOMAS C. CLARKE, OF NEIV YORK, N. Y.

CANTALEVER-BFHDG E.

SPECIFICATION forming part of Letters Patent No. 504,559, datedSeptember 5, 1893.

Application filed August 2, 1892. $erial No. 441,906. (No model.)

To all whom, it may concern.-

Be it known that 1, THOMAS C. CLARKE, of New York city, in the countyand State of New York, have invented a new and useful Improvement inCantalever-Bridges, of which the following is a specification, referencebeing had to the annexed drawings, forming a part thereof, in whichFigure 1 is a side elevation of a bridge without anchorage ties belowthe land span, constructed according to my improvement. Fig. 2 is a sideelevation of a modified form of the bridge, the said bridge beingprovided with anchorage ties below the land span. Fig. 3 is a transversesection taken through the center of the bridge; and Fig. at is a sideelevation of a part of one of the overfloor stays.

Similar letters of reference'indicate corresponding parts in all theviews.

The object of my invention is to construct a cantalever bridge in such amanner as to secure great economy of material and cost.

In carrying out my invention, I make use of the form of cantaleverbridge in which suspended girders are used, the members of which take upthe compression which comes from the ties supported by the towers; Ialso arrange the stays on converging lines to enable them to resist windpressure, and furthermore, I provide an expansion joint by means ofwhich the members of the bridge are allowed to expand or contractwithout in any way interfering with their proper action. I also resistthe bodily movement of the girders from unbalanced loads by a peculiararrangement of the stays.

In the form shown in Fig. 1, the towers a support the girders b, 12 bymeans of the stays c, c, 0 c c 0 The stay 0 is connected with the staysc c on the opposite side of the tower, and in like manner the stay 0 isconnected with the stays 0 c The stays c 0 extend over saddles at thetop of the tower and are connected with the stays c c and c crespectively, in the manner shown in Fig. 4, that is to say, the stayupon one side of the tower is connected with two stays on the oppositeside of the tower by means of eyes and pins; but I do not limit orconfine myself to this particular construction. The lower ends of thestays c are connected with the ends of the girders 7), 12 The stays c, 0are connected with the girders Z), 21 at points between the towers andshore ends of the girders, and the stays c c are connected with thegirders at points located between the tower and the center of thebridge.

In the form shown in Fig. 2, the girders B, B, are suspended from thetowers A, by means of the stays or ties O, C, 0 extending over the floorof the bridge, and connected at different heights with the tower, thestays 0 being preferably connected with the top, and the stays O, 0being connected with the tower at points between the top and the bridgefloor. These stays are made of steel wire cables. The panels forming thegirders B, B, may be constructed on any approved plan. The central loosespan D of the bridge is connected with the girders B, B, by means ofexpansion joints. The stays O, O, 0 are secured to posts E, attached tothe main girder or trestle of the bridge, the said posts serving toprevent the stays from deflection. The steel wire stays which supportthe girders of the bridge are farther apart at the tops of the towersthan at the places of attachment to the girder. The efiect of thisconstruction is to do away with much of the metal ordinarily used incantalever bridges for wind bracing.

Two cases occur in construction; one where tail or land span, Fig. 2,can be supported from below, and here I make the supports, alsoanchorages from the stays G and G This supports the unbalanced loadsbetween the tower and the ends of the cantalever. The other case iswhere no supports can be placed under the tail spans. Here, Fig. 1, Idivide the main anchor stay 0 after it passes over the tower into thetwo smaller intermediate stays c c and in like manner divide the mainstay 0, which supports the center of the girder after it passes over thetower, into two smaller stays c and 0 In this way I avoid an upwardbending movement on the girders and consequent deflection on the otherside of the tower.

By the improvement in cantalever bridges, which I have invented, I amenabled to construct a bridge of longer span than has heretofore beenattempted. This form of cantalever was first suggested by the Frenchengineer Navier, in 1825, and has since been reinvented by the lateProfessor Trowbridge, and others, since then under the name of derrickcantalevers. This form of bridge has never been brought into practicaluse for two reasons; one is, because in cantalever spans of moderatelength, say below one thousand feet, the present system of diagonallybraced girders is preferable, while for very long spans, the derrick isimpracticable. If the inclined ties were made of pins and eye-bars,their width in long spans, owing to the number of members required,would be so great as to cover the whole width of the bridge, renderingit impossible to attach them to the lower compression members. Theirweight would be prohibitory, and the surface exposed to wind pressurevery great. They would be very difficult to support and impossible toerect without staging. I avoid all these difficulties by making theinclined ties of small cables made of steel wires laid up parallel andunite them after erection. This material has a tensilestrength of onehundred and eighty-five thousand pounds per square inch, or three timesas much as the eye-bar and pin system. This allows of a great reductionof the area and weight. It can be easily put in place; it requires fewersupports; it exposes less surface to the wind, and it can be easily andstrongly attached to the compression members without taking up too muchspace laterally. This application of steel wire to form the inclinedties of derrick cantalever bridges presents advantages over every otherknown system of construction.

The second objection to the derrick cantalever is that under a movingload it is nearly as flexible as a suspension bridge. The tie on oneside of the tower goes down with the load becauseit pulls up on theother side, be ing resisted only by the stiffness of the girders. Theonly remedy heretofore proposed has been to anchor the land spans atevery point of attachment of the ties.

In many cases anchors cannot be used.

My device has the advantage of being capable of gathering all theintermediate ties supporting one side of the bridge into one at the topof the tower. This single tie on the land side is attached to theanchorage at the end of the girder, and on the river side to the otherend girder which supports the central loose span.

In my improved bridge the pull is always against the weight which issufficient to resist an upward movement.

Having thus described my invention, I claim as new and desire to secureby Letters Patent- 1. A cantalever bridge in which the main land anchorstays pass over the towers and are thence divided into the intermediatestays on the water or central side, and in which the main stay on thecentral or water side, after passing over the tower is divided into theintermediate stays on the land side.

2. A cantalever bridge, provided with intermediate stays on the landside, said stays being anchored from below, substantially as specified.

THOMAS C. CLARKE.

Witnesses:

G. SEDGWICK, E. M. CLARK.

